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Search Results: 1 - 10 of 200510 matches for " Alleyna P. Claxton "
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Ethnic Variation in Inflammatory Profile in Tuberculosis
Anna K. Coussens,Robert J. Wilkinson,Vladyslav Nikolayevskyy,Paul T. Elkington,Yasmeen Hanifa,Kamrul Islam,Peter M. Timms,Graham H. Bothamley,Alleyna P. Claxton,Geoffrey E. Packe,Mathina Darmalingam,Robert N. Davidson,Heather J. Milburn,Lucy V. Baker,Richard D. Barker,Francis A. Drobniewski,Charles A. Mein,Leena Bhaw-Rosun,Rosamond A. Nuamah,Christopher J. Griffiths,Adrian R. Martineau
PLOS Pathogens , 2013, DOI: 10.1371/journal.ppat.1003468
Abstract: Distinct phylogenetic lineages of Mycobacterium tuberculosis (MTB) cause disease in patients of particular genetic ancestry, and elicit different patterns of cytokine and chemokine secretion when cultured with human macrophages in vitro. Circulating and antigen-stimulated concentrations of these inflammatory mediators might therefore be expected to vary significantly between tuberculosis patients of different ethnic origin. Studies to characterise such variation, and to determine whether it relates to host or bacillary factors, have not been conducted. We therefore compared circulating and antigen-stimulated concentrations of 43 inflammatory mediators and 14 haematological parameters (inflammatory profile) in 45 pulmonary tuberculosis patients of African ancestry vs. 83 patients of Eurasian ancestry in London, UK, and investigated the influence of bacillary and host genotype on these profiles. Despite having similar demographic and clinical characteristics, patients of differing ancestry exhibited distinct inflammatory profiles at presentation: those of African ancestry had lower neutrophil counts, lower serum concentrations of CCL2, CCL11 and vitamin D binding protein (DBP) but higher serum CCL5 concentrations and higher antigen-stimulated IL-1 receptor antagonist and IL-12 secretion. These differences associated with ethnic variation in host DBP genotype, but not with ethnic variation in MTB strain. Ethnic differences in inflammatory profile became more marked following initiation of antimicrobial therapy, and immunological correlates of speed of elimination of MTB from the sputum differed between patients of African vs. Eurasian ancestry. Our study demonstrates a hitherto unappreciated degree of ethnic heterogeneity in inflammatory profile in tuberculosis patients that associates primarily with ethnic variation in host, rather than bacillary, genotype. Candidate immunodiagnostics and immunological biomarkers of response to antimicrobial therapy should be derived and validated in tuberculosis patients of different ethnic origin.
Electric field gradients from first-principles and point-ion calculations
E. P. Stoll,P. F. Meier,T. A. Claxton
Physics , 2001, DOI: 10.1103/PhysRevB.65.064532
Abstract: Point-ion models have been extensively used to determine "hole numbers" at copper and oxygen sites in high-temperature superconducting cuprate compounds from measured nuclear quadrupole frequencies. The present study assesses the reliability of point-ion models to predict electric field gradients accurately and also the implicit assumption that the values can be calculated from the "holes" and not the total electronic structure. First-principles cluster calculations using basis sets centred on the nuclei have enabled the determination of the charge and spin density distribution in the CuO2-plane. The contributions to the electric field gradients and the magnetic hyperfine couplings are analysed in detail. In particular they are partitioned into regions in an attempt to find a correlation with the most commonly used point-ion model, the Sternheimer equation which depends on the two parameters R and gamma. Our most optimistic objective was to find expressions for these parameters, which would improve our understanding of them, but although estimates of the R parameter were encouraging the method used to obtain the gamma parameter indicate that the two parameters may not be independent. The problem seems to stem from the covalently bonded nature of the CuO2-planes in these structures which severely questions using the Sternheimer equation for such crystals, since its derivation is heavily reliant on the application of perturbation theory to predominantly ionic structures. Furthermore it is shown that the complementary contributions of electrons and holes in an isolated ion cannot be applied to estimates of electric field gradients at copper and oxygen nuclei in cuprates.
“Window Shopping, Granada, 1930s”
Mae Claxton
Transatlantica : Revue d'études Américaines , 2010,
Abstract: “Window Shopping, Granada, 1930s,” Photographs, p. 16, with the gracious permission of the Eudora Welty FoundationAn African American woman, dressed in her Saturday go-to-town-best, stands outside a store window, chin in hand, contemplating the contents in the window. The image is reflective and thoughtful. What is she thinking? And what lies beyond the frame of this photograph? In Mississippi in the 1930s, could she walk into this store, perhaps try on clothes or hats, and make a purchase? I...
First-Principles Calculation of Electric Field Gradients and Hyperfine Couplings in YBa2Cu3O7
S. Renold,S. Plibersek,E. P. Stoll,T. A. Claxton,P. F. Meier
Physics , 2001, DOI: 10.1007/s100510170077
Abstract: The local electronic structure of YBa2Cu3O7 has been calculated using first-principles cluster methods. Several clusters embedded in an appropriate background potential have been investigated. The electric field gradients at the copper and oxygen sites are determined and compared to previous theoretical calculations and experiments. Spin polarized calculations with different spin multiplicities have enabled a detailed study of the spin density distribution to be made and a simultaneous determination of magnetic hyperfine coupling parameters. The contributions from on-site and transferred hyperfine fields have been disentangled with the conclusion that the transferred spin densities essentially are due to nearest neighbour copper ions only with marginal influence of ions further away. This implies that the variant temperature dependencies of the planar copper and oxygen NMR spin-lattice relaxation rates are only compatible with commensurate antiferromagnetic correlations. The theoretical hyperfine parameters are compared with those derived from experimental data.
'Alveolar recruitment strategy' improves arterial oxygenation after cardiopulmonary bypass
B A Claxton, J Berridge, P Morgan, H McKeague, A Mulpur
Critical Care , 2001, DOI: 10.1186/cc1438
Abstract: We tested the effect of an 'alveolar recruitment strategy' on arterial oxygenation in a prospective, randomised, controlled study of 78 patients undergoing cardiopulmonary bypass. Divided equally into three groups of 26, Group 'No PEEP' received standard post bypass manual lung inflation, and no PEEP applied until on ICU. Group '5 PEEP' received standard post bypass manual inflation, and then 5 cmH2O PEEP applied and maintained until extubation on ICU. The third group 'treatment group', received a pressure controlled stepwise increase in PEEP up to 15 cmH2O and tidal volumes of 18 ml/kg or a peak inspiratory pressure of 40 cmH2O was reached. This was maintained for 10 cycles, and the PEEP of 5 cmH2O was maintained until extubation on ICU. Arterial blood samples were analysed at 30 min post induction of anaesthesia, and then at 30 min, 1, 2 and 6 hours post bypass. The length of ICU stay, hospital stay and incidence of chest infections was recorded.In both the zero PEEP and 5 PEEP groups there was a decrease in arterial oxygenation at 30 min post bypass (mean decrease of 15.5 and 15.0 respectively), however in the treatment group there was an increase in oxygenation compared to baseline at 30 min (mean increase of 1.9). The difference between the treatment group and the other two control groups was very significant at 30 min with P < 0.001. At 1 h post bypass the difference was significant at P = 0.002 for the no PEEP group and P = 0.04 for the 5 PEEP group (Fig. 1). No significant difference was found between the two control groups. At 2 and 6 hours post bypass there was not a significant difference between the three groups. There was no significant difference in ICU stay, hospital stay or incidence postoperative chest infections. No complications due to the alveolar manoeuvre occurred.We conclude that the application of an alveolar recruitment strategy improves arterial oxygenation up to one hour after cardiopulmonary bypass surgery. We hypothesize that this improv
Young tableaux, multi-segments, and PBW bases
John Claxton,Peter Tingley
Mathematics , 2015,
Abstract: The crystals for finite dimensional representations of sl(n+1) can be realized using Young tableaux. The infinity crystal on the other hand is naturally realized using multisegments, and there is a simple description of the embedding of each finite crystal into the infinity crystal in terms of these realizations. The infinity crystal is also parameterized by Lusztig's PBW basis with respect to any reduced expression for the longest word in the Weyl group. We give an explicit description of the unique crystal isomorphism from PBW bases to multisegments for one standard choice of reduced expression, thus obtaining simple formulas for the actions of all crystal operators on this PBW basis. Our proofs use the fact that the twists of the crystal operators by Kashiwara's involution also have simple descriptions in terms of multisegments, and a characterization of the infinity crystal due to Kashiwara and Saito. These results are to varying extents known to experts, but we do not think there is a self-contained exposition of this material in the literature, and our proof of the relationship between multi-segments and PBW bases seems to be new.
Keeping hospice palliative care volunteers on board: Dealing with issues of volunteer attrition, stress, and retention
Claxton-Oldfield Stephen,Claxton-Oldfield Jane
Indian Journal of Palliative Care , 2008,
Abstract: This article explores the issues of hospice palliative care volunteer attrition and retention (i.e., why volunteers leave and how to keep them interested). In addition, common sources of stress for volunteers will be identified and suggestions for alleviating stress will be offered. Volunteers are special people; patients and families greatly appreciate the care and support they provide and the other staff members′ (e.g., nurses) jobs are often made easier because of them. Thus, maintaining a committed group of volunteers is an extremely important task for volunteer coordinators. The literature reviewed in this article focused mostly on North American studies and was limited to research that specifically involved hospice palliative care volunteers as participants.
Module structure of interphotoreceptor retinoid-binding protein (IRBP) may provide bases for its complex role in the visual cycle – structure/function study of Xenopus IRBP
Federico Gonzalez-Fernandez, Claxton A Baer, Debashis Ghosh
BMC Biochemistry , 2007, DOI: 10.1186/1471-2091-8-15
Abstract: The full-length Xenopus IRBP cDNA codes for a polypeptide of 1,197 amino acid residues beginning with a signal peptide followed by four homologous modules each ~300 amino acid residues in length. Modules 1 and 3 are more closely related to each other than either is to modules 2 and 4. Modules 1 and 4 are most similar to the N- and C-terminal modules of the two module IRBP of teleosts. Our data are consistent with the model that vertebrate IRBPs arose through two genetic duplication events, but that the middle two modules were lost during the evolution of the ray finned fish. The sequence of the expressed full-length IRBP was confirmed by liquid chromatography-tandem mass spectrometry. The recombinant full-length Xenopus IRBP bound all-trans retinol and 11-cis retinaldehyde at 3 to 4 sites with Kd's of 0.2 to 0.3 μM, and was active in protecting all-trans retinol from degradation. Module 2 showed selectivity for all-trans retinol over 11-cis retinaldehyde. The binding data are correlated to the results of docking of all-trans-retinol to the crystal structure of Xenopus module 2 suggesting two ligand-binding sites. However, homology modeling of modules 1, 3 and 4 indicate that both sites may not be available for binding of ligands in all four modules.Although its four modules are homologous and each capable of supporting ligand-binding activity, structural differences between their ligand-binding domains, and interactions between the modules themselves will be critical to understanding IRBP's complex role in the visual cycle.The transport of retinoids and fatty acids between the retinal pigment epithelium (RPE) and retina is critical to photoreceptor development, structure and function. The exchange of visual cycle retinoids and possibly fatty acids between these two cell layers is mediated by interphotoreceptor retinoid-binding protein (IRBP) [reviewed in [1-5]]. IRBP is the most abundant protein component of the interphotoreceptor matrix, the extracellular material
Impact of enteral protein supplementation in premature infants
Barrus DM, Romano-Keeler J, Carr C, Segebarth K, Claxton B, Walsh WF, Flakoll PJ
Research and Reports in Neonatology , 2012, DOI: http://dx.doi.org/10.2147/RRN.S27358
Abstract: ct of enteral protein supplementation in premature infants Original Research (1715) Total Article Views Authors: Barrus DM, Romano-Keeler J, Carr C, Segebarth K, Claxton B, Walsh WF, Flakoll PJ Published Date June 2012 Volume 2012:2 Pages 25 - 31 DOI: http://dx.doi.org/10.2147/RRN.S27358 Received: 15 October 2011 Accepted: 01 December 2011 Published: 01 June 2012 David M Barrus1, Joann Romano-Keeler2, Christopher Carr3, Kira Segebarth4, Betty Claxton2, William F Walsh2, Paul J Flakoll5 1Department of Neonatology, Saint Francis Hospital–Bartlett, Memphis, TN, 2Department of Pediatrics, Vanderbilt Medical Center, Nashville, TN, 3Department of Surgery, Naval Hospital Bremerton, Bremerton, WA, 4Pediatric and Diabetes Specialists, Carolinas Medical Center, Charlotte, NC, 5Department of Surgery, Vanderbilt Medical Center, Nashville, TN, USA Objective: The quantity of enteral protein supplementation required by premature infants to optimize growth has not been determined. This study compares the growth of premature infants fed the current standard intake of protein (3.5 g/kg/day) with the growth of those fed a higher amount (4.0 g/kg/day). Study design: Fifty-two infants <1500 g and <33 weeks gestational age participated in a blinded, single-center, prospective randomized control trial to compare growth between two groups of different protein-intake levels. Primary outcomes were average daily weight gain (g/kg/day), head-circumference (cm/kg/week) and linear growth velocity (cm/kg/week). Secondary outcomes were serum indices of protein tolerance and plasma amino acid concentrations. Results: Infants receiving higher amounts of protein had higher rates of growth for body weight (18.2 ± 0.7 versus 16.2 ± 1.0 g/kg/day; P < 0.05) and head circumference (0.87 ± 0.08 versus 0.62 ± 0.07 cm/kg/week; P < 0.05), with no differences in blood protein or plasma amino acid concentrations. Length of hospital stay was 14 days shorter for the higher-protein group (51.4 ± 4.0 versus 65.9 ± 6.3 days). Conclusion: Increasing premature infant enteral protein supplementation from a calculated intake of 3.5–4.0 g/kg/day improved growth in a safe manner.
Newly Standing Infants Increase Postural Stability When Performing a Supra-Postural Task
Laura J. Claxton, Jeffrey M. Haddad, Katelyn Ponto, Joong Hyun Ryu, Sean C. Newcomer
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0071288
Abstract: Independent stance is one of the most difficult motor milestones to achieve. Newly standing infants exhibit exaggerated body movements and can only stand for a brief amount of time. Given the difficult nature of bipedal stance, these unstable characteristics are slow to improve. However, we demonstrate that infants can increase their stability when engaged in a standing goal-directed task. Infants' balance was measured while standing and while standing and holding a visually attractive toy. When holding the toy, infants stood for a longer period of time, exhibited less body sway, and more mature postural dynamics. These results demonstrate that even with limited standing experience, infants can stabilize posture to facilitate performance of a concurrent task.
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